A teller at a drive-up window at a bank had the following service times (in minutes) for 20 randomly selected customers:

SAMPLE
1	2	3	4
4.5	4.6	4.5	4.7
4.2	4.5	4.6	4.6
4.2	4.4	4.4	4.8
4.3	4.7	4.4	4.5
4.3	4.3	4.6	4.9

1) What is the probability of a Type I error for these 3-sigma control limits?

Select one:

a.

99.74%

b.

None of the other options.

c.

95.44%

d.

0.26%

e.

4.55%

2) If the process parameters are unknown, estimate its mean and standard deviation. (That is, find the average and standard deviation of all data points at once.)

Select one:

a.

x_bar = 4.3, s = 0.19

b.

x_bar = 4.5, s = 0.0368

c.

x_bar = 4.3, s= 0.0368

d.

x_bar = 4.5, s = 0.19

e.

x_bar = 4.7, s = 0.0368

f.

None of the other options.

g.

x_bar = 4.7, s = 0.19

3) What is sX?

Select one:

a.

0.08584

b.

0.04292

c.

0.009597

d.

None of the other options.

e.

0.09597

f.

0.047986

g.

0.016476

h.

0.03839

i.

0.007368